POST UTME BABCOCK UNIVERSITY 2019 Chemistry | Objective

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Question 1
Determine the number of moles of $\text{CO}_2$ produced when 2.50 g of $\text{CaC}_2$ is decomposed according to the equation $\text{CaC}_2(s) \rightarrow \text{Ca}(s) + \text{C}(s) + \text{CO}_2(g)$.
A. 0.0250 mol
Correct B. 0.0500 mol
C. 0.100 mol
D. 0.200 mol

Correct Answer: B

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Question 2
A 25.0 mL sample of a solution containing $\text{Fe}^{2+}$ ions is titrated with 0.100 M $\text{KMnO}_4$ solution. The reaction is $\text{MnO}_4^- + 5\text{Fe}^{2+} + 8\text{H}^+ \rightarrow \text{Mn}^{2+} + 5\text{Fe}^{3+} + 4\text{H}_2\text{O}$. If 25.0 mL of $\text{KMnO}_4$ solution is required to reach the \endpoint, what is the concentration of $\text{Fe}^{2+}$ ions in the original solution?
A. 0.100 M
B. 0.200 M
Correct C. 0.500 M
D. 1.00 M

Correct Answer: C

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Question 3
A diagram of a titration setup is shown below. If 25.0 mL of 0.100 M $\text{HCl}$ is added to 25.0 mL of 0.100 M $\text{NaOH}$, what is the pH of the resulting solution?
A. 7.00
Correct B. 8.00
C. 9.00
D. 10.0

Correct Answer: B

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Question 4
A 50.0 mL sample of a solution containing $\text{Cu}^{2+}$ ions is titrated with 0.100 M $\text{NaOH}$ solution. The reaction is $\text{Cu}^{2+} + 2\text{OH}^- \rightarrow \text{Cu(OH)}_2(s)$. If 20.0 mL of $\text{NaOH}$ solution is required to reach the \endpoint, what is the concentration of $\text{Cu}^{2+}$ ions in the original solution?
A. 0.100 M
Correct B. 0.200 M
C. 0.500 M
D. 1.00 M

Correct Answer: B

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Question 5
A diagram of a titration setup is shown below. If 25.0 mL of 0.100 M $\text{HCl}$ is added to 25.0 mL of 0.100 M $\text{NaOH}$, what is the pH of the resulting solution?
A. 7.00
Correct B. 8.00
C. 9.00
D. 10.0

Correct Answer: B

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Question 6
Calculate the s\tandard enthalpy change (ΔH) for the reaction: 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s). Given that the s\tandard enthalpy of formation of Al2O3(s) is -1675.7 kJ/mol and the s\tandard enthalpy of formation of Fe(s) is -0.45 kJ/mol. Assume that the s\tandard enthalpy of formation of Al(s) is 0 kJ/mol and that of Fe2O3(s) is -826.4 kJ/mol.
Correct A. -1592.4 kJ/mol
B. -1592.9 kJ/mol
C. -1593.1 kJ/mol
D. -1593.5 kJ/mol

Correct Answer: A

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Question 7
A 0.5 M solution of NaOH is mixed with a 0.2 M solution of HCl. Calculate the pH of the resulting solution.
A. 1.3
Correct B. 1.5
C. 1.7
D. 1.9

Correct Answer: B

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Question 8
The solubility product cons\tant (Ksp) of AgCl is 1.8 × 10^\( -10 \). Calculate the molar solubility of AgCl.
A. 1.6 × 10^\( -5 \) M
Correct B. 1.8 × 10^\( -5 \) M
C. 2.0 × 10^\( -5 \) M
D. 2.2 × 10^\( -5 \) M

Correct Answer: B

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Question 9
A metal M has a density of 8.5 g/cm^3 and a molar mass of 120 g/mol. Calculate the number of moles of M present in 25.0 g of the metal.
A. 0.21 mol
Correct B. 0.22 mol
C. 0.23 mol
D. 0.24 mol

Correct Answer: B

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Question 10
A 2.0 M solution of H2SO4 is mixed with a 1.0 M solution of NaOH. Calculate the pH of the resulting solution.
A. 1.3
Correct B. 1.5
C. 1.7
D. 1.9

Correct Answer: B

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Question 11
The polymerization of styrene to polystyrene is an example of a ______________ reaction.
A. chain reaction
B. step-growth reaction
C. condensation reaction
Correct D. addition reaction

Correct Answer: D

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Question 12
The s\tandard enthalpy of formation of CO2(g) is ______________ kJ/mol.
Correct A. -393.5
B. 393.5
C. -393.5 kJ/mol
D. 393.5 kJ/mol

Correct Answer: A

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Question 13
The rate cons\tant for a first-order reaction is ______________.
Correct A. k = ln[A]t
B. k = [A]t
C. k = 1/t
D. k = t/[A]

Correct Answer: A

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Question 14
The half-life of a radioactive subs\tance is ______________.
Correct A. t1/2 = ln2/k
B. t1/2 = k/ln2
C. t1/2 = k/[A]0
D. t1/2 = [A]0/k

Correct Answer: A

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Question 15
The equilibrium cons\tant for a reaction is ______________.
A. K = [C]^2/[A]^2
Correct B. K = [C]/[A]
C. K = [A]/[C]
D. K = [A]^2/[C]^2

Correct Answer: B

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Question 16
The polymerization of styrene to polystyrene involves the addition of a monomer unit to the growing polymer chain. If the initial concentration of styrene is 2.5 M and the reaction is 50% complete, what is the concentration of the monomer unit added to the polymer chain?
Correct A. 1.25 M
B. 2.5 M
C. 5 M
D. 10 M

Correct Answer: A

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Question 17
A 2.5 M solution of sodium hydroxide (NaOH) is electrolyzed u\sing a platinum electrode. If the reaction is 75% complete, what is the concentration of sodium hydroxide remaining in the solution?
Correct A. 0.625 M
B. 1.25 M
C. 2.5 M
D. 5 M

Correct Answer: A

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Question 18
The atomic radius of an atom is the dis\tance from the nucleus to the outermost electron. If the atomic radius of an atom is 1.5 Å, what is the atomic radius in picometers?
Correct A. 150 pm
B. 200 pm
C. 250 pm
D. 300 pm

Correct Answer: A

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Question 19
A 2.5 M solution of sulfuric acid (H2SO4) is electrolyzed u\sing a platinum electrode. If the reaction is 50% complete, what is the concentration of sulfuric acid remaining in the solution?
Correct A. 1.25 M
B. 2.5 M
C. 5 M
D. 10 M

Correct Answer: A

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Question 20
The molar mass of a subs\tance is the mass of one mole of the subs\tance. If the molar mass of a subs\tance is 50 g/mol, what is the mass of 2 moles of the subs\tance?
Correct A. 100 g
B. 200 g
C. 300 g
D. 400 g

Correct Answer: A

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Question 21
A 2.5 L sample of an ideal gas at 27°C and 1.5 atm is compressed to 0.5 L at cons\tant temperature. Calculate the work done on the gas.
Correct A. -3.375 kJ
B. -1.6875 kJ
C. -2.8125 kJ
D. -4.6875 kJ

Correct Answer: A

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Question 22
A solution of 0.1 M HCl is titrated with 0.1 M NaOH. Calculate the pH after 25 mL of NaOH has been added.
A. 2.00
Correct B. 3.00
C. 4.00
D. 5.00

Correct Answer: B

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Question 23
A 1.0 L sample of a solution containing 0.1 M HCl and 0.1 M NaOH is titrated with 0.1 M HCl. Calculate the pH after 25 mL of HCl has been added.
A. 1.00
B. 2.00
Correct C. 3.00
D. 4.00

Correct Answer: C

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Question 24
A 2.0 L sample of a solution containing 0.1 M HCl and 0.1 M NaOH is titrated with 0.1 M HCl. Calculate the pH after 50 mL of HCl has been added.
A. 1.00
B. 2.00
C. 3.00
Correct D. 4.00

Correct Answer: D

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Question 25
A 1.0 L sample of a solution containing 0.1 M HCl and 0.1 M NaOH is titrated with 0.1 M HCl. Calculate the pH after 100 mL of HCl has been added.
A. 1.00
B. 2.00
C. 3.00
Correct D. 4.00

Correct Answer: D

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